We usually think food and drugs as two different categories. But on a surprising note, there are many similarities between the two. They are both substances you put in your body. Both of them have harmful impact on the body. There has been plenty of research into this and many parallel reasons have been studied on how both, drugs and junk food equally harm your body.
Why we get addicted to these?
The human tongue craves for good taste to satisfy the needs of the brain and stomach - one of the main reasons for junk food addiction. The problem starts where we struggle to cut down on consumption of junk food or lose the control of eating too much of it. Foods that usually harm your body have many similarities. Like most of them contain fat and high quantities of sugar, more carbohydrates and less proteins. All of these are usually highly processed and contain preservatives which in turn contain harmful chemicals. Junk food increases count of fat in body, raises the blood sugar levels and slows down the immunity process of our body.
Why is healthy food non-addictive?
Healthy food is either eaten raw or cooked on instant and consumed. There aren't any preservatives added as these do not undergo high processing. They have their own taste and aren't added with additional flavors for the human body and brain to get addicted to. 
What is the science behind addictive food?
It usually contains snacks, sodas, street food or packaged food. These items can be easily consumed and are absorbed rapidly (just like drugs). Anything that is processed, on high consumption gets addictive. Fried chicken is more addictive than grilled chicken as the amount of fat present is higher in fried chicken. Coca leaves are not addictive, but the processed form that is cocaine, it dangerously addictive. Have you ever wondered why we prefer oreo biscuits over oat digestive biscuits? It is because oroe biscuits contain high flavor and cream which is the processed form of milk.
How to not be an addict?
It isn't easy to stop a bad habit. But it's easy to try. If you are an addict, then you can start with binge eating cucumber slices. They are light for the body and provide lots of nutrition. They will help you avoid binge eating chips. Next, try consuming preservative free food. Instead of drinking packaged juices, try drinking freshly prepared juices. You can also try eating citrus fruits and vegetables that have high content of vitamin C. They help in detoxification of the body. Avoid fried food, instead go for grilled.
If junk food hits the body like a drug, avoid treating it like one.